Certain types of trailers are used for transporting goods from a manufacturing or storage facility to a number of distribution points, such as for example, restaurants, schools or other institutions. The trailers typically have doors in the rear and/or on the sides which allow for loading and unloading of the goods from the trailer. In particular, the goods are typically loaded into the rear of the trailer at the manufacturing or storage facility, and then selected portions are unloaded at each distribution point from either the rear or the side of the trailer, depending on the location of the goods in the trailer for the particular distribution point.
Some trailers are designed to transport both frozen and refrigerated goods. Consequently, trailers can include a refrigeration unit to maintain a reduced temperature in the interior cavity of the trailer. However, the refrigeration unit typically only provides a single controlled temperature, and it is therefor necessary to transport both the frozen and refrigerated goods at the same temperature. Typically, a compromise is made and a temperature is chosen somewhere between the refrigerated temperature and the frozen temperature. However, this compromise temperature is not particularly suited to maintain the quality and integrity of either the frozen or refrigerated goods over long periods of time.
Multi-temperature trailers have been designed which separate the frozen goods from the refrigerated goods during transportation. The multi-temperature trailers typically have a lateral bulkhead separating a front section from a rear section, and a refrigeration device for providing variable air flow for the two sections. For example, Wehby, U.S. Pat. No. 2,677,244, discloses a trailer having a series of moveable lateral bulkheads which separate the interior of the trailer into multi-temperature sections. A refrigeration device provides refrigerated air to the different sections through spaced outlets formed in air ducts. The outlets are selectively controllable to vary the air flow into the sections.
Providing lateral bulkheads in a trailer, however, can complicate the loading and unloading of the goods stored in the front section. In particular, in the case of a trailer with only a rear door, practically all the goods in the rear section must be unloaded first before the goods in the front section are unloaded. If the sections are maintained at different temperatures, for example if the rear section is maintained at a refrigerated temperature, then practically all the refrigerated goods must be unloaded at each distribution point before any of the frozen goods can be unloaded. This manner of loading and unloading is inefficient if many distribution points are scheduled.
Trailers with multi-temperature sections have been designed with doors located on the side of the trailer to facilitate loading and unloading of the forward sections, as shown in Wehby, U.S. Pat. No. 2,633,714. A pull-out platform and step are typically located at the openings in the sides to facilitate using hand trucks or dollies to unload the cargo. However, it can be necessary to lift or push the cargo onto the platform, and then lift and carry the cargo off the ramp and load the cargo onto the handtruck or dolly on the ground. Such manual lifting can increase the risk of accident and can cause fatigue or physical injury. Moreover, having multiple door openings increases the difficulty of maintaining a reduced temperature in the interior of the trailer.
Other trailers have been designed that have selectively moveable panels forming a plurality of compartments which allow loading and unloading of the cargo from the rear of the trailer. For example, Bettker, Jr., et al. U.S. Patent No. 4,221,421, discloses independently moveable rigid panels which can be selectively arranged on mechanical linkages to divide the vehicle body into multiple compartments. The panels in Bettker may be located in a first position juxtaposed parallel to a wall, a second position parallel to and spaced from the wall, or in a third position arranged at an angle to the wall. A single refrigeration unit provides airflow through two ducts, wherein the first duct provides a general air outlet for one compartment, while the second duct provides selectively controllable air outlets for the remaining compartments.
While the foregoing references attempt to provide a method of dividing the interior of a trailer, they are not without drawbacks. For example, in Bettker, the dimensional variation of each compartment is limited to the extent of the movement of the panels on the mechanical linkages. Moreover, the Bettker and the Wehby references disclose a single source of air flow into the interior of the trailer, and although directed through multiple air ducts, the air flow tends to reach an equilibrium across the interior because of the lack of isolated compartments and closed fluid circuits to provide independent air flow to each compartment.